Rope shovels dated from the end of XIX century (steam shovels) have evolved wherein the assembly of the equipment and all of the respective components thereof have steadily increased in size and capacities over time.
Thus, those buckets which in its early stages were built by means of riveting led to welded components thereby allowing to increase its capabilities.
Then, when the dimensions thereof increased significantly there was a forced use of more resistant components having greater thicknesses which at present are obtained by means of hot casting and forging processes.
Even though current buckets include the use of metal plates, these are used in places where the structure is lighter and also as coatings which are resistant to wear.
Nowadays, the use of metal plates is not an alternative for building the whole assembly, since the cast and wrought pieces which are the ones dominating and providing the structural resistance have a greater importance.
Considering the mechanical stresses which these components are subjected to, some of them being wrought and others cast, it becomes necessary to have more complex alloys which in its composition can include several expensive components such as nickel and manganese just to name of few.
The manufacturing processes of these components are also complex.
On the one hand, they require relatively developed technologies in order to keep the manufacture of big pieces under control, which have demanding specifications with regard to its mechanical stresses and on the other hand big non serial individual pieces, involving large amounts of energy which is comparatively artisanal in contrast to the laminating process of plates, are obtained.
From an industrial and economic point of view these mining buckets of a large size are like a “technological craft” which is limited to a few manufacturers having the appropriate installations in order to produce them, wherein the offer is relatively limited and the delivery times of said equipment are very long and very expensive.
In order to better understand the aforementioned it is possible to compare a typical big bucket whose weight is approximately 100 metric tons and with a price in the market of around US 2500, that is, a component of a value of US 25 per kilogram of steel, built as a bucket, versus laminated plates having a high mechanical resistance and also to wear which are commercialize per kilogram for less than one tenth of the calculated value for the kilogram of a bucket.
For any skilled person in the art of metal mechanical manufacture it will result obvious that if someone can obtain an equivalent equipment, mainly built by means of metal plates, said person will have to face a shift paradigm or quantum leap at least with respect to the costs in manufacturing the same.
In the state of the art there are several documents disclosing buckets which have been built by means of casting and forging.
Thus, for instance, document US 2013136570 discloses a bail for a rope shovel having a hoist rope and a dipper. The bail includes a pair of arms coupled to the dipper; and a cross-member extending between the pair of arms and being pivotably coupled to each of the arms. The bail having a cross-member which includes a mounting block for coupling the hoist rope to said bail.
Document US 2012279095 discloses a dipper having an inlet and an outlet, and an inlet reference plane being defined at the inlet. The dipper includes a front wall and an opposite back wall extending between the inlet and the outlet.
A front wall reference plane extends from the inlet to the outlet and is positioned between the front wall and the back wall.
The dipper further includes two side walls connected between the front wall and the back wall and extending between the inlet and the outlet.
The inlet has an inlet area in the inlet reference plane, wherein the outlet has an outlet area in an outlet reference plane substantially parallel to the inlet reference plane.
The front wall, the back wall, and the two side walls are arranged such that the outlet area is at least 3 percent and no more than 25 percent greater than the inlet area.
Document U.S. Pat. No. 7,096,610 discloses a dipper assembly which includes a dipper, a dipper door, and a closure mechanism. The dipper door is pivotally linked relative to the dipper, and has a closed position in which the dipper door closes the open bottom. The closure mechanism has a lock position and an unlock position, and is fixed relative to the dipper and linked to the dipper door. In the lock position, the closure mechanism holds the dipper door in the closed position. In the unlock position, the closure mechanism allows the dipper door to swing away from the closed position.
Document U.S. Pat. No. 5,063,694 discloses an excavating dipper for use with power shovels, draglines and the like that is fabricated from steel plate and is formed to have a separable bottom body member, which may be replaced when worn.
The dipper is of lightweight steel plate construction fabricated into substantially all welded top and bottom body members.
The plate members forming the side and bottom walls of the bottom body member are reinforced by longitudinal and transverse girth ribs.
Document U.S. Pat. No. 4,939,855 discloses an excavating dipper or bucket for a power shovel formed by an upper bucket portion having support brackets and the strength to support the rated load of the dipper and a disposable lower portion having opposed sidewalls and a bottom wall of a material thickness less than the upper sidewalls and top wall.
The lower sidewalls are secured to the upper sidewalls by interference fitted retaining pins disposed in machined bores formed in the upper sidewalls and the lower sidewalls, respectively.
The upper sidewalls may be modified to provide spaced-apart plate members which define a slot for receiving the lower sidewall portions, respectively.
Other documents showing different types of buckets are disclosed in documents U.S. Pat. Nos. 4,517,756; 4,251,933; 4,443,957; 3,402,486; 3,107,445; 2,584,416; 2,561,518; 2,243,965 U.S. Pat. Nos. 1,984,322; 1,757,328; 1,717,907; 1,582,577; 1,539,863; 1,479,340 which are hereby incorporated as reference.
Most of said buckets are manufactured by means of hot casting or forging processes.
However, for instance, document U.S. Pat. No. 2,243,965 discloses a dipper dated from 1940 in which the side and back walls are formed by a bent single plate and the rest of the components are built by the traditional casting and forging methods.
However, this dipper is not able to lift large loads which nowadays are moved in great mining.
Due to the aforementioned, the first objective of the present invention is providing a bucket for a rope shovel solely built by means of laminated steel plates.
A second objective of the present invention is providing components for said bucket, solely built by a plurality of plates where manufacturing costs and times are considerably reduced.
A third objective of the present invention is providing a bucket built by means of cold forming of multiples cylinder plates constituting wide curves where sharp edges are avoided since they cause stress concentration.
A fourth objective of the present invention is providing a bucket which, by virtue of its tubular construction avoids the confluence of welded connections of more than two plates or parts in a same corner, wherein said connections can be distributed in such a way that more than two plates cannot converge in a same place.
A fifth objective of the present invention is providing a bucket which, by virtue of its tubular construction, it simplifies the parts thereof, thereby reducing the quantity of complex welded connections.